JPH1092256A - Switch input device for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the continuous malfunction of a load by inputting the output of an input level judging circuit and the output of an input voltage level monitoring circuit to a logical control circuit, and judging whether a switch is set to the on-state or a switch line is short-circuited. SOLUTION: A switch 1 grounded on one-end side is connected to an electronic unit 20 via a switch line 4, and the power from a battery power supply 60 is fed to a load 3. In this switch input device for an automobile, a diode 30 is connected in series to the switch 1 as an element, the cathode side is connected to the ground side, and a constant voltage effect is generated when the switch 1 is turned on. An input level judging circuit 40 provided in the electronic unit 20 judges whether the input level of the switch line 4 is high or low. An input voltage level monitoring circuit 50 monitors the voltage of the switch line 4. The outputs P1 , P2 of both circuits are inputted to a logical control circuit 90, and the switch 1 is judged to be turned off when both outputs are at a high level, and the switch line 4 is judged to be short-circuited 5 when both outputs are at a low level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switch input device for an automobile having one end grounded.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional switch input device for an automobile. The switch input device for a vehicle includes a switch 1 having one connected to the ground and the other connected to an electronic unit 10. The electronic unit 10 is a switch 1
The load 3 is operated via the output circuit 2 in accordance with ON / OFF of the load.

[0003]

However, in the conventional switch input device for a vehicle, when the switch line 4 is shorted and grounded, the electronic unit 10 cannot be determined to be in the ON state. There is a problem that the load 3 is operated by recognizing that the load 3 is turned on. If the driver does not notice this abnormality, there is a problem that the battery runs down due to continuous operation of the load.

[0004]

SUMMARY OF THE INVENTION The present invention provides a switch input device for a vehicle which solves the above-mentioned problems. The configuration of the switch input device for a vehicle having one end grounded is provided. The input device includes an element connected in series with the switch, which generates a constant voltage effect when the switch is turned on, an input level determination circuit for detecting whether the switch line is at a high level or a low level, and an input voltage for monitoring the voltage of the switch line. A level monitoring circuit, and a logic control circuit that determines whether the switch is ON or the switch line is short based on an output signal from the input level determination circuit and an output signal from the input voltage level monitoring circuit. (Claim 1).

The time constant of the noise elimination filter of the input voltage level monitoring circuit is made larger than the time constant of the noise elimination filter of the input level discrimination circuit. .

Further, the logic control circuit monitors the chattering time from the output from the input level determining circuit and the output from the input voltage level monitoring circuit, and if the time is equal to or longer than a predetermined time, determines that the switch line is in a short-circuit state. (Claim 3).

An input level determining circuit for detecting whether a switch line is at a high level or a low level,
When an input voltage level monitoring circuit that monitors the voltage of the switch line is used, and a logic control circuit is configured to determine whether the switch is ON or the switch line is short by using outputs from both circuits, It is possible to reliably determine whether the switch is ON or the switch line is short-circuited.

Further, when the time constant of the noise elimination filter of the input voltage level monitoring circuit is made larger than the time constant of the noise elimination filter of the input level discrimination circuit, erroneous detection is prevented. be able to.

Further, even if the chattering time of the output signal from the input level discriminating circuit and the output signal from the input voltage level monitoring circuit is monitored by the logic control circuit, the switch is surely turned on. It is possible to determine whether the state is the short state of the switch line.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. This switch input device for a vehicle includes a switch 1 having one connected to the ground and the other connected to the electronic unit 20. A diode 30 is connected to the switch 1 in series. The diode 30
The cathode side is connected to the ground side.

The electronic unit 20 includes an input level determining circuit 40 and an input voltage level monitoring circuit 50.

The input level discrimination circuit 40 has an input pull-up resistor 41 which is supplied with power from a battery power supply 60 and applies a voltage to the switch 1. Further, it has a comparator 80 that connects the output terminal of the input pull-up resistor 41 and the control power supply 70. The output signal of the comparator 80 is input to the logic control circuit 90.

The switch line 4 in which the switch 1 and the diode 30 are connected in series is connected to the output terminal side of the input pull-up resistor 41.

In the above circuit configuration, the logic control circuit 9
A high-level voltage is applied to the input terminal of 0 when the switch 1 is OFF, and a low-level voltage is applied to the input terminal of ON. The logic control circuit recognizes the high-level voltage as 1 and the low-level voltage as 0, and switches the switch. 1 is OFF or ON
Recognize whether it is.

However, in the above circuit configuration, even if the switch line 4 is short-circuited 5 and grounded, the switch 1
Is ON, a low-level voltage is applied to the input terminal of the logic control circuit 90, and the logic control circuit recognizes that the switch 1 is ON.

Therefore, in the present invention, an input voltage level monitoring circuit 50 is further added. The input voltage level monitoring circuit 50 has a comparator 100, which is connected to the switch line 4 and the control power supply 70. The output signal of the comparator 100 is input to the logic control circuit 90.

FIG. 2 shows the threshold value V of the comparator 80.
The relationship between + h1, the threshold value V + h2 of the comparator 100, the switch ON / OFF, and the respective voltage levels when the switch line 4 is short-circuited 5 is shown.

The input voltage level monitoring circuit 5 as described above
At 0, a high level voltage is applied both when the switch 1 is OFF and when the switch 1 is ON.
The high level voltage is recognized as 1. However, when the switch line 4 is short-circuited 5, the output of the comparator 100 becomes a low level voltage, so that the logic control circuit 90 recognizes 0.

Accordingly, as shown in FIG. 3, when the logic control circuit 90 recognizes that the output signal P1 of the comparator 80 is 0 and the output signal P2 of the comparator 100 is also 0, the switch line 4 is short-circuited 5. It is time. Note that, as shown in FIG.
When 1 is 1 and the output signal P2 of the comparator 100 is also 1, the switch 1 is OFF, and when the output signal P1 of the comparator 80 is 0 and when the output signal P2 of the comparator 100 is 1, the switch is turned off. 1 is ON.

By increasing the time constant of the noise elimination filter of the input voltage level monitoring circuit 50 with respect to the time constant of the noise elimination filter of the input level discriminating circuit 40, the noise caused by the switch line 4 can be reduced. Erroneous detection can be effectively prevented.

In some cases, the ground potential is not 0 V but has a certain potential. To absorb such a potential difference, two diodes are arranged in series with the switch 1 or a Zener is used. It is preferable to arrange the diode so that the anode side is connected to the ground side. In this case, the input level discriminating circuit is a microcomputer or C
Since a low level cannot be detected with a high level / low level determination threshold voltage of a buffer circuit such as a MOS, a comparator or an analog input circuit must be used.

The logic control circuit monitors the chattering time of the output signal from the input level discriminating circuit and the output signal from the input voltage level monitoring circuit. You may make it. In particular, by monitoring the chattering time of the output signal from the input voltage level monitoring circuit,
It is possible to detect that the wire harness has begun to interfere with the vehicle body, to diagnose the wire harness, and to perform maintenance before a serious problem occurs.

In the present invention, a comparator is used for each of the input level discriminating circuit 40 and the input voltage level monitoring circuit 50, but these circuit components are not particularly limited.

[0024]

As described above, the switch input device for a vehicle according to the present invention is a switch input device for a vehicle having one end grounded, wherein the switch input device for a vehicle is connected in series with the switch to turn on the switch. An element that sometimes produces a constant voltage effect, an input level discriminating circuit that detects whether the switch line is at a high level or a low level, an input voltage level monitoring circuit that monitors the voltage of the switch line, and an output from the input level discriminating circuit A logic control circuit for determining whether the switch is in the ON state or the short-circuit state of the switch line based on the signal and the output signal from the input voltage level monitoring circuit. And whether the switch line is short-circuited.

Further, by making the time constant of the noise elimination filter of the input voltage level monitoring circuit larger than the time constant of the noise elimination filter of the input level determination circuit, erroneous detection can be effectively prevented. .

Further, the logic control circuit monitors the chattering time from the output from the input level determining circuit and the output from the input voltage level monitoring circuit, and if the time is longer than a predetermined time, determines that the switch line is in the short-circuit state. Therefore, it is possible to reliably determine whether the switch is ON or the switch line is short-circuited.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a switch input device for a vehicle according to the present invention.

FIG. 2 is a diagram showing a relationship between voltage levels of each comparator in FIG. 1;

FIG. 3 is an explanatory diagram showing a determination state in a logic control circuit.

FIG. 4 is a circuit configuration diagram of a conventional automotive switch input device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Switch 20 Electronic unit 30 Diode 40 Input level judgment circuit 50 Input voltage level monitoring circuit 60 Battery power supply 70 Control power supply 80 Comparator 90 Logic control circuit 100 Comparator

Claims (3)

[Claims] 1. An automotive switch input device having one end grounded, wherein the automotive switch input device comprises:
An element that is connected in series with the switch and generates a certain voltage effect when the switch is turned on, an input level determination circuit that detects whether the switch line is at a high level or a low level, and an input voltage level monitoring circuit that monitors the voltage of the switch line ,
A switch input for an automobile, comprising: a logic control circuit that determines whether the switch is ON or the switch line is short based on an output signal from an input level determination circuit and an output signal from an input voltage level monitoring circuit. apparatus. 2. The automotive switch according to claim 1, wherein the time constant of the noise removal filter of the input voltage level monitoring circuit is made larger than the time constant of the noise removal filter of the input level determination circuit. Input device. 3. A logic control circuit monitors a chattering time of an output signal from an input level determination circuit and an output signal from an input voltage level monitoring circuit, and determines that a switch line is short-circuited if the time is equal to or longer than a predetermined time. The switch input device for a vehicle according to claim 1 or 2, wherein